Many industrial processes require mixing of a first set of components to form a second set of components and then mixing or applying the second set of components in a particular manner to produce the finished product. For instance, in the manufacture of different shades of roofing shingles, different colors of granite granules are each placed in a separate silo. Several different colors are mixed to create three or four color combinations. Each separate color combination is transported to a separate dispensing bin, and the color combinations making up one shingle shade are then applied to an asphalt-coated fiberglass mat in a particular manner and sequence to provide shingles having the desired shade.
The silos holding the pure colors of granite granules have a proportion gate and a slide gate damper to control the output of the silo. Each color combination has a particular formula, and the proportion gates of the silos containing the required colors of granite granules must be set to provide the proper proportion of each individual color. When the dampers are opened, the granite granules from the chosen silos fall onto a conveyor and are mixed thereon. The color combination of granite granules is transported to a dispensing bin and held pending distribution onto the asphalt-coated mat. A second color combination is then mixed and transported to a second bin and, in most cases, third, fourth and fifth combinations are transported to third, fourth and fifth bins. Thus, each time a different color combination is to be mixed, the individual proportion gates must be adjusted and the slide gate dampers opened or closed to provide the proper formulation of each individual granite color to the mixture. Previously, workers at the plant adjusted the proportion gates and the slide gate dampers so that human error and negligence as well as the absence of simultaneous opening and closing of the slide gate dampers resulted in a slightly different color combination each time a specific combination was made.
The prior system also suffered from human error when providing the color combination to the appropriate bin because workers had to manually adjust a lazy susan in order to put the appropriate color combination into a specific bin. An inattentive worker often mistakenly placed the lazy susan outlet over the wrong input port or would turn the lazy susan while the color combination was flowing, thus causing granite granules to fall into several of the bins. Furthermore, the dispensing bins often ran out of one color combination before the run was finished so that either the shingles had a different shade for the remainder of that particular lot or the entire operation had to be shut down to permit mixing of a small amount of the needed granite granule combination to complete the run. Of course, because of human error this also resulted in a slightly different shade of shingle because the new color combination would have a slightly different color from the original color combination.